Is it possible to omit my son-in-law from our will without excluding our daughter as well?

You could also bypass the son-in-law and give some funds directly to the grandchildren {immediately if they are over 18, or in a trust if they are minors, or you do not want them to have the $ until they are older ... 21 ... 25...}

I think most inheritances flow down to the descendants [and adoptees] of the will maker.

What everyone failed to mention is that your son in law is married to your daughter. If you leave something to your daughter he wants badly enough, then he simply files for divorce and gets half. This is marital property. And prenups do not cover post nuptual.

So how to do this? Well you'd have to hide it in a cave somewhere and not tell your son in law about it. That's about it.

You can omit your son-in-law but your daughter is married to him so all of their assets are combined legally. They are one financial entity legally. She is responsible for his debts, she can be required to care for him if he is incapacitated, what's hers is his and vice versa. You would most likely have to set up some sort of trust to keep him from getting anything should they divorce, but you can not stop her from sharing the proceeds of your will with him if she so desires while they are still married.

Yes, you just don't include him in the will. Normally, unless you have something specific you want to leave to a daughter or son-in-law, you wouldn't include them anyway. In most states, inheritance property is not considered joint marital property unless you daughter co-mingles those assets with her spouse.

For example, if you leave her the house, and they both move into it and live there for a while, it will become a joint asset and in the case of divorce he will have claim to part of it. If you leave her money and she deposits it into a joint account, it will become a joint martial asset. Basically, it will depend on how she treats these assets after you die as to whether he gets any part of them. So long as she keeps them separate and doesn't use them in a way which makes them joint assets, in most states she keeps them in the case of divorce.

your daughter should be named, and don't name the son in law. if you want to control how your daughter spends this money, have a trust specify that the money is to be use by your daughter and not by any other person

Absolutely you can. My children are all married but I do not mention their husbands in my will. I received a couple of condos and an investment account from my father. I keep them in my name only. They are not community property.

Yes

To make sure he does not get anything you cash word the will in such a way that it can not be shared

Yes, but your daughter will share what she gets with him.

Yes, but there's nothing to stop her from sharing what you leave her with him.

Of course. Just don't name him.